Clinical and Hematological Parameters and Their Correlation With the Severity of Vitamin B12 Deficiency: A...

Background Vitamin B12 is an essential micronutrient for optimal hematopoietic and neurocognitive function. Vitamin B12 deficiency is associated with a wide spectrum of diseases affecting various systems of the body. This study aimed to investigate the clinico-hematological parameters in patients with vitamin B12 deficiency and analyze their correlation with severity. Methodology This hospital-based, prospective observational study was conducted at the Department of Pathology, Tata Main Hospital, Jamshedpur, over 12 months (June 2022-May 2023). Vitamin B12 testing was not routinely performed for all OPD and IPD patients but was ordered based on clinical discretion; therefore, patients with serum vitamin B12 <180 pg/mL were included, regardless of anemia status. During the study period, a total of 420 adult patients were classified as deficient (100-179 pg/mL) or severely deficient (<100 pg/mL). Sociodemographic, clinical, and hematological parameters were collected and analyzed for correlation with the severity of vitamin B12 deficiency. Results Among 9,596 patients tested for vitamin B12, 2,193 had levels <180 pg/mL, giving a prevalence of 22.9% among tested individuals. Out of 420 patients who met our eligibility criteria, 268 participants (63.8%) were classified as vitamin B12 deficient, while 152 participants (36.2%) were severely deficient. The most common clinical features were pallor (236, 56.2%), fatigue (160, 38.10%), anorexia (156, 37.14%), and tingling sensations (135, 32.14%). Anemia was present in 315 participants (75%), with higher rates of moderate and severe anemia in the severely deficient group (P < 0.001). Contrary to expectations, normocytic normochromic blood picture (176, 41.90%) and normocytic normochromic anemia (126, 30.00%) were more common than macrocytic anemia (9, 2.14%). The proportion of patients with irritability, numbness, and glossitis was significantly higher in severely deficient patients (P < 0.05). Mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and red cell distribution width (RDW) values were significantly higher in the severely deficient group (P < 0.05). Bicytopenia and pancytopenia were observed in 11 patients (2.6%) and 10 patients (2.38%), respectively, and occurred exclusively in those with severe vitamin B12 deficiency. Conclusions Vitamin B12 deficiency has a significant prevalence with distinct clinico-hematological correlations to severity. The correlation between the severity of deficiency and clinical manifestations, particularly neurological symptoms and the degree of anemia, underscores the importance of early detection and treatment. The predominance of normocytic rather than macrocytic anemia challenges traditional diagnostic paradigms and suggests clinicians should not rely solely on macrocytosis when suspecting vitamin B12 deficiency.